If you saw any of the hundreds of manipulated cartoons, film posters and photographs of chief executive hopeful Henry Tang Ying-yen being shared online during last year's election, you were part of a brave new world of art that is challenging social norms, political control and the definition of art itself. Or so say proponents of social media art - art that uses sites such as Facebook, Twitter, Snapchat and Tumblr as its medium of creation and dissemination.

During last year's election, Tang, who illegally added an underground expansion to his luxury home, was made fun of in numerous cartoons and satirical works, including one online poster where Tang's face grins from a Harry Potter movie spoof below the caption "Kowloon Basement and the Chamber of Secrets".

Amusing, but is it art? Yes, say artists and art critics, for two reasons.

First, as Hong Kong gallery owner and critic John Batten says: "Andy Warhol demonstrated that anything could be art - the use of the internet is just an extension of that idea."

Second, when it comes to social media art, according to one definition hashed out during an artists' roundtable discussion on the Facebook page of New York City-based blogazine Hyperallergic, the artwork in question is not one satirically altered movie poster, but the collective activity of multiple, at times anonymous, artists. Often they are just members of the public not practising or trained in art, all working on the same meme - in this case, Henry Tang's illegal basement. One can hardly dispute that it is a wonderfully witty and creative outpouring.

At the heart of the issue is the slight but important distinction between art on social media, and social media art. An artist painting a picture, photographing it and putting it up on Facebook, or making a video, uploading it to YouTube, and tweeting the link is not social media art. The medium needs to be integrated into the work.

Take the meme of the Pepper Spray Cop that spread through the internet last year. A row of seated protesters at the University of California were showered with pepper spray by a policeman, Lieutenant John Pike. The image of Pike, spray can in hand, was posted on social news website Reddit. The next day, two Photoshopped images appeared online, one with another meme, the image of actor Leonardo DiCaprio walking jauntily, known as Strutting Leo, Photoshopped over Pike.

The second image saw Pike superimposed into the 1819 painting Declaration of Independence by John Trumbull.

As news of the pepper spray incident circulated on television, in newspapers and on online news sites, the meme spread. Soon, hundreds of Photoshopped images were shared, including Pike superimposed into Picasso's famous anti-war painting Guernica and on to an image of the United States Constitution.

The social media artwork here is not an original, authentic image, or the individual images created based on this original, but the diverse, creative collection of works.

"A social media artwork can have collective authorship," says American artist An Xiao Mina, one of the artists involved in trying to define social media art during the Hyperallergic roundtable discussion. "This is different from having an anonymous author or no author. Although the Pepper Spray Cop meme can be identified to a couple of posts that launched the meme, the original authors haven't been identified. The merits of this activity as an art form are debatable, but it's no question to me that the collective activity was more interesting than any individual image or video."

In social media art, the web is not only involved in the sourcing and marketing of the art, but also its expression. An Xiao and the other artists in the Hyperallergic group identified three other characteristics: that the art involves the audience in some fashion as it is inherently a social medium; that the art is accessible beyond a "typical" art world audience while still being conceptually rich; and that, ultimately, the art is all about the artist's intent, and it should be judged accordingly.

Judging social media art, which is inherently plural and shifting, is tricky. While An Xiao says that critiquing a social media art piece involves the same process as other art forms - understanding the artist's intent, and assessing how successfully the artist has achieved this - Joanie San Chirico, another of the Hyperallergic roundtable artists, points out that the audience's influence can alter a piece.

"The artist's intent has to be fluid and may even transform before the completion of the work." Also, when there are multiple, anonymous artists, involved, intent can differ, and be unknown. As mainland artist Ma Yongfeng says: "Everyone can be an artist in today's world; this means you don't need anyone to endorse you as qualified as a social media artist. As everybody can be a social engine, so the artist's identity is not important now. What's critical is that you can provide new energy for this over-institutionalised society. People use this tool to create, protest and demonstrate … maybe one day they [can] really change something."

Critics point to the banality of social media art. Paddy Johnson, art editor at online The L Magazine, states: "Much social media art, while refreshingly clear in intent - statements written by artists working with social media are actually a joy to read - often lacks the creative juice that defines truly great art." There is, however, no doubt social media art can be powerful. When social media art takes place in the field of social or political commentary, it is at its most exciting. Mainland artist Ai Weiwei continues to provoke authorities with his art, which includes the use of social media, such as his political take on South Korean musician Psy's Gangnam Style song and video, which went globally viral. Of course, using popular media for propaganda is nothing new. "The Philippines and texting was a much earlier exponent - earlier than Ai - of political messaging using social-type media," Batten says. "It's similar to the dropping from a plane of propaganda material over enemy territory during wartime. The mainland sent similar messages by balloon over Taiwan during the Cultural Revolution. Same idea, different media."

The idea may be nothing new, but the media seems to be working. The posters and cartoons ridiculing Tang allowed the public to voice their discontent and disseminate it, further swaying public opinion. Tang, once thought to be the favoured contender in the chief executive race, could only sit back and watch as his candidacy unravelled.